Bone plate assembly provided with screw locking mechanisms

ABSTRACT

One embodiment of the present invention is directed to a bone plate assembly that includes a bone plate, bone screw(s) received in aperture(s) in the bone plate, and screw fixation member(s). The screw fixation member(s) may, alone or in conjunction with the bone plate, fix the bone screw(s) in place when such bone screw(s) are inserted in the aperture(s) in the bone plate. In one example (which example is intended to be illustrative and not restrictive) when the bone screw(s) have been received by the bone plate and inserted into bone and/or tissue, the bone plate assembly can-be used to fuse anatomical structures together (such as adjoining bones) and/or to heal a fracture in bone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Application Ser. No. 60/421,819, filed Oct. 28, 2002.

FIELD OF THE INVENTION

One embodiment of the present invention is directed to a bone plateassembly that includes a bone plate, bone screw(s) received inaperture(s) in the bone plate, and screw fixation member(s). The screwfixation member(s) may, alone or in conjunction with the bone plate, fixthe bone screw(s) in place when such bone screw(s) are inserted in theaperture(s) in the bone plate. In one example (which example is intendedto be illustrative and not restrictive) when the bone screw(s) have beenreceived by the bone plate and inserted into bone and/or tissue, thebone plate assembly can be used to fuse anatomical structures together(such as adjoining bones) and/or to heal a fracture in bone.

BACKGROUND OF THE INVENTION

Bone plate assemblies are employed in order to fuse bones or to repairfractures in bones. For example, U.S. Pat. No. 6,413,259, incorporatedherein by reference, discloses embodiments for bone plates.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is directed to an arrangementfor fixing, in a vertebrate, a screw inserted through a plate. In oneexample (which example is intended to be illustrative and notrestrictive) a bone plate assembly according to the present inventionmay have at least two bone screws, each received in at least twoapertures in the bone plate. The bone plate assembly may also have screwfixation members provided for the bone screws. When the bone screws areinserted through the apertures in the bone plate, and installed in boneand/or tissue at a preselected angle, the presence of the screw fixationmembers may aid in fixing the bone screws in place. Each bone screw mayhave a head, sized so that the head does not pass through the boneplate, and a shank provided with threads (e.g., which threads may extendsubstantially to the tip of the bone screw). In yet another embodiment,the bone plate assembly may be provided with washers (e.g., for eachscrew employed in the assembly) that reside in the apertures in the boneplate. In yet another embodiment, each washer may be provided with anaperture in which the bone screw is received, when the bone screw isinserted into the bone plate. In yet another embodiment, after the bonescrew is received in the aperture in the washer, and inserted in boneand/or tissue, the washer may be actuated to fix the angle at which thebone screw has been inserted (e.g., relative to the bone plate).

In a further embodiment, the washer may be provided with a sidewall,which sidewall defines the aperture though which the bone screw extends.The sidewall may have a thickness that varies with respect to theposition along the washer's perimeter. In one embodiment, the washer maybe provided with a first sidewall region on its perimeter that isrelatively thicker than a second sidewall region.

In yet another embodiment, one or more apertures of the bone plate maybe provided with a recess that is cut into the sidewall that defines theaperture in the bone plate. The depth to which the recess is cut mayvary around the perimeter of the recess. In yet another embodiment, afirst region of the recess may have a depth that is greater than asecond region of the recess. In yet another embodiment, a washer mayreside partially or fully within the recess.

In yet another embodiment, the washer may reside in the recess, alignedso that the first relatively thicker sidewall region of the washer ispositioned within the first relatively deeper region of the recess, andthe second relatively thinner sidewall region of the washer ispositioned in the second relatively shallower region of the recess.After the bone screw is received in the aperture in the washer, andinserted in bone and/or tissue, the washer may be actuated to fix theangle at which the bone screw has been inserted (e.g., relative to thebone plate). The bone screw may be fixed by rotating the washer, therebymoving the first relatively thicker sidewall region of the washer intothe second relatively shallower region of the recess, which effectivelycauses the first relatively thicker sidewall region to extend laterally,into the aperture in the bone plate, where the washer impinges againstthe bone screw (e.g., the head of the bone screw), applying a forcethereto which wedges the bone screw between the washer and the oppositesidewall of the aperture. This operation thus fixes the bone screw inplace, retaining it at a particular angle (e.g., the at which the bonescrew is inserted).

In yet another embodiment, the present invention may allow for the bonescrew(s) to toggle (i.e., move within a confined range) after beinginstalled through the bone plate and being held by the washer. This canbe arranged, for example, by actuating the washer to an intermediateposition, which allows the screw to toggle.

In yet a further embodiment of the present invention, a bone plateassembly may be provided in which the bone plate assembly may include abone plate, bone screw(s) received in aperture(s) in the bone plate, andwasher(s). The washer(s) may, alone or in conjunction with the boneplate, fix the bone screw(s) in place when the bone screw(s) areinserted in the aperture(s) in the bone plate. Here the washer of thebone plate assembly may be adapted to reside over the bone screw and bejoined therewith in a locking arrangement. In yet another embodiment,the head of the bone screw may be provided with a number of tangs,spaced apart from each other, mounted on the upper surface of the head.The tangs may be mounted upon wedges, which wedges extend up from thehead of the screw. The wedges may be not as wide as the tangs, and maybe narrowed by an undercut.

In a further embodiment, the washer may be provided with a washer bodythrough which a central opening is provided. A number of lobes may beprovided on the periphery of the central opening. In one example (whichexample is intended to be illustrative and not restrictive) three lobesare provided (it should be understood that other arrangements are, ofcourse, possible). In yet another embodiment, the washer may also beprovided with splays which are provided on the exterior of the washer.The splays may be separated from the remainder of the washer body bytracks, which tracks extend into the washer body.

In yet another embodiment, the washer and the wedges and/or tangs may bedesigned to engage with each other in a locking arrangement. Relative toeach other, the wedges may be slightly wider than the width of at leasta portion of the track.

In yet another embodiment, when the bone plate assembly is implanted ina person, the bone plate may be positioned on the bone, tissue and bone,or tissue to be joined by the bone plate. The bone screw may be insertedthrough the aperture in the bone plate and installed in bone and/ortissue by known techniques. The bone screw may be installed at apreselected angle, relative to the bone plate. To fix the screw at theangle at which it is installed, the washer may be placed over the headof the bone screw, and positioned so that the wedges are poised to enterthe track portions. In yet another embodiment of the invention, a toolmay be provided, the tool having a head adapted to fit within thecentral washer opening, which tool then engages with the central washeropening, to rotate the washer. The wedges may thereby enter the trackportions. Since the wedges maybe wider than at least a portion of thetracks, the splays may be forced outward when the wedges enter theintermediate track portion(s). In this arrangement, the splays may beforced into an abutting arrangement with the sidewalls of the aperturein which the bone screw and washer reside. The abutting arrangementbetween the splays and the sidewalls of the aperture may fix the bonescrew at a particular angle (e.g., the angle at which the bone screw wasinstalled).

In yet another embodiment, a bone plate assembly may be generallyprovided with a bone plate, at least two bone screws received inapertures in the bone plate, and moveable doors that fix the bone screwsin place when the bone screws are inserted in the apertures in the boneplate. The bone screw employed in this embodiment may have a head sizedso that the head does not pass through the bone plate. The bone screwmay further have a shank provided with threads (e.g., which threads maythat extend to the tip of the bone screw). In another embodiment, thebone plate assembly may be provided with a cut out portion on its uppersurface, to which the doors are slidably mounted. The cut out portionmay be positioned adjacent the bone screw apertures, at a portion of theedge thereof.

In yet another embodiment, the sliding doors may be dimensioned tosubstantially not cover the apertures in the bone plate in a firstposition (in which first position the bone screws may be installed), yetslide and at least partially cover the apertures once the screws havebeen inserted (to thereby fix the bone screws in place). In yet anotherembodiment, the doors may be positioned in the cut out portion on theupper surface of the bone plate, and may be retained therein by a lipprovided at the upper sidewall of the cut out portion. In yet anotherembodiment, the cut out portion may be sized slightly greater than thesliding doors. Thus, when a bone screw is positioned in the aperture ofthe bone plate, the sliding door can be slid in the direction of thehole, in order to cover the bone screw (and to fix the bone screw inplace).

In yet another embodiment, a bone screw may be provided with a number ofsplays positioned around the periphery of the head of the bone screw.The splays may be mounted upon wedges that extend up from the head ofthe screw. In one embodiment, there is a space between at least aportion of the splay and the head of the bone screw. When the screw isinstalled in an aperture in the bone plate at a preselected angle, atool may be employed to force the splays outward, into a locking andabutting arrangement with the sidewalls of the bone plate aperture. Inyet another embodiment, a cam may be positioned in the interior spacedefined by the splays. When the cam is rotated, the cam may force thesplays outward, into a locking and abutting arrangement with thesidewalls of the bone plate aperture. The presence of the cam mayfurther provide a counterforce, which counterforce may maintain thesplays in the locking and abutting arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of the present invention;

FIG. 2 is a top plan view of the embodiment of FIG. 1;

FIG. 3A is a cross sectional view of the embodiment of FIG. 1;

FIG. 3B is a cross sectional view showing in greater detail the circledportion of FIG. 3A;

FIG. 4A is a cross sectional view of the bone plate of the embodiment ofFIG. 1 (shown across the long side);

FIG. 4B is a cross sectional view showing in greater detail the circledportion of FIG. 4A;

FIG. 5 is a side elevational view of a screw employed in the embodimentof FIG. 1;

FIG. 6 is a cross sectional view of the bone plate of the embodiment ofFIG. 1 (shown across the short side);

FIG. 7A is a top plan view of a washer used in an embodiment of thepresent invention;

FIG. 7B is a perspective view of the washer of FIG. 7A;

FIG. 8A is a cross-sectional view of a tool used in conjunction with theembodiment of FIG. 1;

FIG. 8B is a perspective view of a portion of the tool of FIG. 8A;

FIG. 9 is a cross sectional view of the washer of FIG. 7A;

FIG. 10 is a partially sectioned perspective view of a portion of theembodiment of FIG. 1;

FIG. 11 is a partially sectioned view showing an the undercut or recessin connection with the embodiment of FIG. 1;

FIG. 12A depicts the washer of FIG. 7A in the open or unactuatedposition;

FIG. 12B depicts the washer of FIG. 7A in the closed or actuatedposition;

FIG. 13 is a partially sectioned perspective view of another embodimentof the present invention;

FIG. 14 is a perspective view of a washer and screw of the embodiment ofFIG. 13;

FIG. 15 is a perspective view of the washer of the embodiment of FIG.13;

FIG. 16 is a top plan view showing in greater detail an aspect of thewasher of the embodiment of FIG. 13;

FIG. 17 is a top plan view of the screw of the embodiment of FIG. 13;

FIG. 18 is a side elevational view of the screw of the embodiment ofFIG. 13;

FIG. 19 is a perspective view of the screw of the embodiment of FIG. 13;

FIG. 20 is a cross sectional view of the washer and screw of theembodiment of FIG. 13;

FIG. 21 is a perspective view of the embodiment of FIG. 13, where thewasher has been opened;

FIG. 22A is a top plan view of another embodiment of the presentinvention;

FIG. 22B is a perspective view of the embodiment of FIG. 22A;

FIG. 22C is cross sectional view of the embodiment of FIG. 22A;

FIG. 23 is a perspective view of another embodiment of the presentinvention;

FIG. 24 is top plan view of the embodiment of FIG. 23;

FIG. 25 is a cross sectional view of the embodiment of FIG. 23;

FIG. 26 is a side elevational view of the embodiment of FIG. 23;

FIG. 27 is a perspective view of the embodiment of FIG. 23;

FIG. 28 depicts another embodiment of the present invention;

FIG. 29 depicts, in a perspective view, another embodiment in which adouble lobed washer is employed;

FIG. 30 depicts, in a perspective view, another embodiment in which atri-lobed washer is employed; and

FIG. 31 depicts, in a perspective view, a split-ring washer according toanother embodiment of the present invention.

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingfigures. The figures constitute a part of this specification and includeillustrative embodiments of the present invention and illustrate variousobjects and features thereof.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Referring now generally to FIGS. 1-3, it is seen that a bone plateassembly 10 is provided with bone plate 12, bone screw(s) 14 received inaperture(s) 16 in the bone plate 12, and washer(s) 18 that, alone or inconjunction with the bone plate 12, fix the bone screw(s) 14 in place(e.g., when the bone screw(s) 14 are inserted in the aperture(s) 16 inthe bone plate). Each bone screw 14 has a head 20 sized so that it doesnot pass through the bone plate 12. Further, each bone screw 14 has ashank 22 provided with threads 24 (e.g., which threads 24 may extend totip 26). The head 20 of bone screw 14 is further provided with anopening 15 that is dimensioned to mate with the head of a tool, so thatthe bone screw 14 can be installed in tissue and/or bone. In oneembodiment, the head 20 of the bone screw 14 may be provided withgrooves 21 (see, e.g., FIGS. 3B and 5). Bone plate assembly 10 is alsoprovided with washer(s) 18. Each washer 18 has an opening 19 thoughwhich a bone screw is received (see, e.g., FIG. 3B).

Referring now generally to FIG. 3B, it is seen that each washer 18 isprovided with a sidewall 28 (which sidewall 28 defines the aperture 19though which the bone screw extends) and that the sidewall 28 has avarying thickness with respect to position along the washer's perimeter(see also, for example, FIG. 7A). In one embodiment, the washer 18 isprovided with a first sidewall region 28 a that is relatively thickerthan a second sidewall region 28 b (i.e., in this embodiment dimension“a” is greater than dimension “b” (see FIG. 3B)).

Referring now to FIGS. 7A, 7B, 8A, 8B, 9 and 31, it is seen that inthese examples (which examples are intended to be illustrative and notrestrictive) the washer may be provided with a series of splines 31 thatare spaced at intervals around the inside perimeter of the washer (thewasher of FIG. 31 is similar to the washers of FIGS. 7A, 7B, 8A, 8B and9, with the exception that the washer of FIG. 31 is a split-ringwasher). As depicted in the Figures, the splines may be solid members(which may extend from the perimeter of the washer towards the aperture19 of the washer), and may be spaced apart by openings 32. Thearrangement of the splines 31 and openings 32 may be complementary to aspline 41 and opening 42 arrangement provided on the head 44 of a tool40 (see, e.g., FIGS. 8A and 8B). In operation, when the splines of thewasher are engaged with the spaces of the tool, and vice versa, theapplication of a rotational force to the tool is translated to thewasher, thereby turning the washer. The tool may, for example, beoperated manually by handle 43, or by drill, in which case drill bitreceiving channel 45 may be provided.

Referring once again to FIG. 7A, it is seen that in one example (whichexample is intended to be illustrative and not restrictive) the washer18 may be provided with a detent 50 positioned on the outside of thesidewall 28. In this example, the sidewall of the bone plate may beprovided with an indentation 52, which is sized to receive the detentprovided on the washer 18 (see, e.g., FIG. 10). When the bone plate andwasher are assembled, the washer can be aligned so that the detent 50resides in the indentation 52. This arrangement may inhibit unwantedrotation of the washer (e.g., until the time to actuate it, as describedbelow).

As seen in FIG. 6, bone plate 12 may be constructed with an arcuateshape. Of course, plates with other shapes and/or dimensions arepossible.

In another example (which example is intended to be illustrative and notrestrictive) bone plate 12 may be provided with one or more recesses 30,positioned within the bone plate 12 (see FIGS. 4A, 4B, 5 and 6). Eachrecess 30 may extend around the perimeter of each aperture 16 in thebone plate 12. Each recess 30 may be cut into the sidewall of theapertures in the bone plate 12. The lateral depth to which each recess30 is cut may vary depending on the location on the perimeter of therecess 30. In one example (which example is intended to be illustrativeand not restrictive), a first region 30 a of the recess 30 may have alateral depth that is greater than the lateral depth of a second region30 b of the recess 30 (i.e., in this embodiment dimension “a” is greaterthan dimension “b” (see FIG. 4B)). In another example (which example isintended to be illustrative and not restrictive), the lower portion ofaperture 16 may be provided with a tapered sidewall 16 a against whichthe bottom portion of the screw head 20 may rest (see FIG. 4B). Thewasher 18 may reside within the recess, aligned so that the firstrelatively thicker sidewall region 28 a of the washer 18 is positionedwithin the first relatively deeper region 30 a of the recess, and thesecond relatively thinner sidewall region 28 b of the washer 18 ispositioned in the second relatively shallower region 30 b of the recess.In one embodiment, when the bone screw 14 is inserted into the aperture16 of the bone plate 12, the washer 18 is substantially coplanar withthe head 20 of the bone screw 14.

Referring now to FIG. 11, certain characteristics of the recess 30 asseen from the bottom of the bone plate 12 are shown. As shown here, thelateral depth of the second recess region 30 b may be minimal (and maynot be present at all) and a lateral depth may be provided essentiallyonly in the first recess region 30 a.

Referring now generally to FIGS. 12A and 12B, it is seen that when thebone plate assembly is implanted in a person, the bone plate ispositioned over the bone, bones, and/or tissue to be joined by the boneplate 12. The bone screw(s) are inserted through the aperture(s) in thewasher(s) (which washer(s) may reside in the recess(s) provided in theaperture(s) of the bone plate) and the bone screw(s) are installed inbone and/or tissue by known techniques. Each bone screw may be installedat a preselected angle, relative to the bone plate. In the position inwhich a washer is unlocked, the bone screw may pass through the openingin the washer (e.g., so that the bone screw may be installed at apreselected angle) (see FIG. 12A). To fix the bone screw (e.g., at theangle at which the bone screw is installed), the washer may be actuatedby rotating the washer (e.g., with the tool, as described above). Whenthe washer is rotated, the first relatively thicker sidewall region ofthe washer may move into the second relatively shallower region of therecess. Such movement may effectively cause the first relatively thickersidewall region to extend laterally into the aperture in the bone plate(where the relatively thicker sidewall region impinges against the headof the bone screw, thereby applying a force thereto which wedges thebone screw between the washer and the opposite sidewall of the aperture)(see FIG. 12B). Such wedging of the bone screw may fix the bone screw atan angle (e.g., the angle at which the bone screw was inserted). FIGS.10 and 12B depict the condition where the bone screw is wedged afteractuating the washer.

In yet another embodiment of the present invention, depicted in FIGS.13-21, another bone plate assembly is depicted. Shown here is a boneplate, bone screw, and a washer. With this arrangement, a bone platethat does not have a recess can be employed with this screw and washerpairing.

More particularly, FIG. 13 depicts a bone plate assembly 100, generallyprovided with bone plate 102, bone screw(s) 104 received in aperture(s)106 in the bone plate 102, and washer(s) 108 that, alone or inconjunction with the bone plate 102, fix the bone screw(s) 104 in place(i.e., when the bone screw(s) 104 are inserted in the aperture(s) 106 inthe bone plate 102). Each bone screw 104 has a head 110 sized so that itdoes not pass through the bone plate 102. Further, each bone screw 104has a shank 112 provided with threads 114 (e.g., which threads 114extend to tip 116). In one embodiment, the head 110 of each bone screw104 may be provided with grooves 118 (see, e.g., FIGS. 4 and 5C). Boneplate assembly 100 is provided with washer(s) 108, each of which (asdescribed below) is adapted to reside over a bone screw 104 and bejoined therewith in a locking arrangement.

As shown in FIGS. 13 and 17-19, for example, in this embodiment the head110 of bone screw 104 is provided with a number of tangs 120, spacedapart from each other, mounted on the upper surface of the head 110. Thetangs 120 include wedges 122, which wedges 122 are not as wide as theupper portions of the tangs 120 (the wedges 122 are 5 narrowed by anundercut). The head 110 is provided with an opening 107 in which a toolcan be received to apply a rotational force, which rotational forcepermits the installation of the screw in tissue and/or bone.

Each washer 108 is sized and dimensioned to fit within one of theaperture(s) 106 in the bone plate 102. Each washer 108 is provided witha washer body 124 through 10 which a central opening 125 is provided. Anumber of lobes 126 are provided on the periphery of the central opening125. As depicted in the embodiment of FIG. 14, for example, three lobesare provided, though it should be understood that other arrangements arepossible. Each washer 108 is also provided with splays 127, which areprovided on the exterior of the washer 108. The splays 127 are separatedfrom the remainder of the washer body 124 by tracks 128, which tracks128 extend into the washer body 124. The tracks 128 are provided with anentrance portion 130, an intermediate track portion 132, and a terminus134. The entrance portion 130 and the terminus 134 are wider than theintermediate track portion 132. The width of the intermediate trackportion 132 is narrowed by the presence of nubs 136 that extend into thetrack (e.g., from the washer body 124 and/or the splays 128).

The washer 108 and the wedges 122/tangs 120 are designed to engage witheach other in a locking arrangement. Relative to each other, the wedges122 are slightly wider than the width of at least the intermediate trackportion 132.

In operation, when the bone plate assembly is implanted in a person, thebone plate is positioned over the bone, bones, and/or tissue to bejoined by/to the bone plate. The bone screw(s) are inserted through theaperture(s) in the bone plate and installed in bone and/or tissue byknown techniques. Each bone screw may be installed at a preselectedangle, relative to the bone plate. To fix the bone screw at apreselected angle (e.g., the angle at which the bone screw isinstalled), the washer is placed over the head of the bone screw,positioned so that the wedges 122 are poised to enter the track portions128. A tool, provided with a head adapted to fit within the centralwasher opening 125 and lobes 126 is inserted into the washer, which isthen rotated. The wedges 122 thereby enter the track portions 128. Sincewedges 122 are wider than at least the intermediate track portions 132,the splays 127 are forced outward when the wedges enter the intermediatetrack portions 132 (see, e.g., FIG. 21). The splays are forced into anabutting arrangement with the sidewalls of the aperture in which thebone screw 106 and washer reside 108. The abutting arrangement betweenthe splays 127 and the sidewalls of the bone plate 102 fixes the bonescrew 104 (e.g., at the angle at which the bone screw 104 wasinstalled).

In another example (which example is intended to be illustrative and notrestrictive) the splays 127 may enter an undercut 140 in the aperture(s)106 (see, e.g., FIG. 13).

In another embodiment FIG. 29 depicts, in a perspective view, a doublelobed washer. The double lobed washer may be shaped differently than therecess and/or aperture in the bone plate which received the washer. Whenthe washer is rotated, it is deformed, compressing it against the bonescrew, fixing the angle of the bone screw (e.g., the angle at which thebone screw is inserted). The embodiment of FIG. 30 is similar. FIG. 30depicts, in a perspective view, a tri-lobed washer. Again, the tri-lobedwasher may be shaped differently than the recess and/or aperture in thebone plate. When the washer is rotated, it is deformed, compressing itagainst the bone screw and fixing the angle of the bone screw (e.g., theangle at which the bone screw is inserted). The embodiments of FIGS. 29and 30 may thus operate without a recess.

In another embodiment, shown in FIGS. 22A, 22B and 22C, there is shown abone plate assembly 150, generally provided with bone plate 152, bonescrew(s) 154 (which bone screw(s) 154 are received in aperture(s) 156 inthe bone plate 152), and 25 moveable doors 158 (which moveable doors 158may slide and may fix the bone screw(s) 154 in place when the bonescrew(s) 154 are inserted in the aperture(s) 156 in the bone plate 152).Each bone screw 154 has a head sized so that the head does not passthrough the bone plate 152. Further, each bone screw 154 has a shankprovided with threads that extend to a tip. In one example (whichexample is intended to be illustrative and not restrictive), the head ofthe bone screw may be provided with grooves. Bone plate assembly 150 isprovided with cut out portion(s) 164, on an upper surface of the boneplate assembly 150, to which the moving doors 158 are slidably mounted.The cut out portion(s) 164 are positioned adjacent the aperture(s) 156,at a segment of the edge thereof.

In one example (which example is intended to be illustrative and notrestrictive), each moveable door 158 is provided with two substantiallyflat sides 166,167, cutouts of partial circles 168, full cut out circle169, and arcuate side 172. It should be apparent that other dimensionalarrangements are possible. The moveable doors 158 are positioned in thecut out portion(s) 164 on the upper surfaced of the bone plate 152, andare retained therein by lip 174 provided at the upper sidewall of thecut out portion 164. Dovetail undercuts may also be present along otherupper sidewalls to maintain the doors in place. The cut out portion(s)164 are sized slightly greater than the moveable doors. Thus, when eachbone screw is positioned in an aperture 156 of the bone plate 152, themoveable door 158 can be slid in the direction of the aperture 156, inorder to cover the bone screw 154 (and thus fix the bone screw 154 inplace).

Referring now to FIG. 22C, in one example (which example is intended tobe illustrative and not restrictive) a channel 180 is fully or partiallybored into the bone plate 152 at a location between the cut outportions(s) 164. Still referring to FIG. 22C, in another example (whichexample is intended to be illustrative and not restrictive) the moveabledoors 158 are provided with stops 182 that depend from the doors, intothe channel 180. When the door is moved into the locked position, asshown in the left hand side of FIG. 22C, the stop engages channelsidewall 184, inhibiting further movement of the door. Detents 186 andindentations 188 may also be used if desired.

Another embodiment of the present invention is depicted in FIGS. 23-27.In this embodiment a bone screw 200 is provided with a head 202 sized sothat it does not pass through a bone plate (not shown) and shank 204provided with threads (not shown) that extend to tip 208. In one example(which example is intended to be illustrative and not restrictive), thehead 202 of the bone screw 200 may be provided with grooves (not shown).

As seen in these Figures, the head 202 of bone screw 200 is providedwith a number of splays 212, spaced apart from each other, and extendingaround the periphery of the head of the bone screw 200. The splays 212are mounted on the upper surface of the head 202, and in one example(which example is intended to be illustrative and not restrictive), mayhave an arcuate shape. Each splay 212 extends around a portion of theperiphery of the head of the bone screw 200. Each splay 212 is mountedupon a wedge 214, (wherein the wedges 214 extend up from the head of thescrew). The wedges 214 join the splay 212 at the base of the splay 212,elevating the splay 212 off of the head of the bone screw 200. Spaces215 are present between the portions of the splay 212, which extend overthe periphery of the head of the bone screw 200, and the head of thebone screw 200 itself.

In this embodiment, after the bone screw 200 has been inserted into anaperture in a bone plate, and installed at a preselected angle, theangle can be fixed by forcing the splays outward (i.e., into a lockingand abutting arrangement with the sidewalls of the aperture in the boneplate). In operation, a tool is inserted into the interior space 216 androtated (to force the splays outward, into an abutting and lockingarrangement with the sidewalls of the apertures).

In another embodiment, shown in FIG. 28, a cam 218 may be utilized. Inone example (which example is intended to be illustrative and notrestrictive), the cam may be rotatably mounted to the head 202 of thebone screw 200. In operation, the splays are forced outward, by rotatingthe cam 218 (which cam 218 moves against the interior walls of thesplays). Here, the cam 218 provides a counterforce against the forceapplied by the sidewalls of the apertures (which counterforcefacilitates the maintaining of the splays 212 in a locking and abuttingarrangement with the sidewalls of the aperture in the bone plate).

In another embodiment one or more of the washers may be a split-ringwasher. While a number of embodiments of the present invention have beendescribed, it is understood that these embodiments are illustrativeonly, and not restrictive, and that many modifications may becomeapparent to those of ordinary skill in the art.

What is claimed is:
 1. A bone screw assembly, comprising: a bone screwwith a head and a shank, which bone screw includes at least one mountingmember extending from the head in a direction generally away from theshank; and a washer with a central opening and an outer periphery, whichwasher includes at least one splay along the outer periphery and atleast one track between the outer periphery and the central opening,wherein the splay is defined by the track; wherein the mounting memberis adapted to operatively engage the track such that rotation of thewasher relative to the bone screw causes the mounting member to forcethe splay outwards, away from the central opening.
 2. The bone screwassembly of claim 1, comprising a plurality of mounting members and arespective plurality of splays and tracks.
 3. The bone screw assembly ofclaim 2, wherein each mounting member is adapted to operatively engage arespective track such that rotation of the washer relative to the bonescrew causes each mounting member to force a respective splay outwards,away from the central opening.
 4. The bone screw assembly of claim 3,wherein each track has a narrowed intermediate portion against whicheach respective mounting member contacts to force each respective splayoutward.
 5. The bone screw assembly of claim 3, wherein the bone screwassembly is adapted to affix an implant member to bone.
 6. The bonescrew assembly of claim 5, wherein the implant member has at least oneaperture extending therethrough and the aperture includes a first regionsized to permit the shank of the bone screw but not the head of the bonescrew to pass through and a second region sized to permit both the shankof the bone screw and the head of the bone screw to pass through.
 7. Thebone screw assembly of claim 6, wherein the washer is sized to passthrough the second region of the implant member but not the first regionof the implant member.
 8. The bone screw assembly of claim 7, wherein afirst interior perimeter surface in the implant member is defined by thefirst region of the aperture, wherein a second interior perimetersurface in the implant member is defined by the second region of theaperture, and wherein each of the mounting members is adapted tooperatively engage a respective track such that rotation of the washerrelative to the bone screw causes each mounting member to force arespective splay outwards, away from the central opening and intocontact with the second interior perimeter surface to fix the bone screwin orientation relative to the implant member.
 9. The bone screwassembly of claim 8, wherein the second interior perimeter surfaceincludes a recess in at least a portion thereof, and wherein each of themounting members is adapted to operatively engage a respective tracksuch that rotation of the washer relative to the bone screw causes eachmounting member to force a respective splay outwards, away from thecentral opening and into contact with the recess to fix the bone screwin orientation relative to the implant member.
 10. The bone screwassembly of claim 8, wherein the bone screw includes grooves, at least aportion of which grooves are brought into contact with the implantmember when each mounting member forces a respective the splay outwards,away from the central opening and into contact with the second interiorperimeter surface.
 11. The bone screw assembly of claim 5, wherein theimplant member has a top surface and a bottom surface, wherein the firstregion of the aperture is adjacent the bottom surface of the implantmember, and wherein the second region of the aperture is adjacent thetop surface of the implant member.
 12. The bone screw assembly of claim11, wherein the first region of the aperture tapers from wider tonarrower in a direction moving from the top surface of the implantmember towards the bottom surface of the implant member.
 13. The bonescrew assembly of claim 12, wherein the bone screw is inserted from thetop surface of the implant member towards the bottom surface of theimplant member.
 14. The bone screw assembly of claim 11, wherein thebottom surface of the implant member is contoured to substantially matcha contour of the bone to which the implant member is affixed.
 15. Thebone screw assembly of claim 5, wherein the implant member is used forperforming at least one of: (a) fusing at least two bones; and (b)healing a fracture in a bone.
 16. The bone screw assembly of claim 1,wherein the head of the bone screw includes a mechanism for engaging adriving tool.
 17. The bone screw assembly of claim 16, wherein themechanism for engaging the driving tool is a hex socket.
 18. The bonescrew assembly of claim 1, wherein the washer includes a mechanism forengaging a driving tool.
 19. The bone screw assembly of claim 18,wherein the mechanism for engaging the driving tool comprises at leastone lobe disposed adjacent the central opening.
 20. A bone screw,comprising: a shank; a head at one end of the shank; and at least onedeformable member attached to the head at a position opposite the shank;wherein the deformable member is adapted to be deformable outwards, awayfrom a central axis of the bone screw.
 21. The bone screw of claim 20,comprising a plurality of deformable members arranged around the head.22. The bone screw of claim 21, wherein the plurality of deformablemembers are arranged around the head to define an interior space. 23.The bone screw of claim 22, further comprising a cam mechanism disposedwithin the interior space.
 24. The bone screw of claim 23, wherein thecam mechanism is configured to deform the deformable members outwardswhen the cam mechanism is rotated relative to the head.
 25. The bonescrew of claim 24, wherein the bone screw is adapted to affix an implantmember to bone.
 26. The bone screw of claim 25, wherein the implantmember has at least one aperture extending therethrough and the apertureincludes a first region sized to permit the shank of the bone screw butnot the head of the bone screw to pass through and a second region sizedto permit both the shank of the bone screw and the head of the bonescrew to pass through.
 27. The bone screw of claim 26, wherein a firstinterior perimeter surface in the implant member is defined by the firstregion of the aperture, wherein a second interior perimeter surface inthe implant member is defined by the second region of the aperture, andwherein each of the deformable members is adapted to deform outwards,when the cam is rotated relative to the head, to come into contact withthe second interior perimeter surface to fix the bone screw inorientation relative to the implant member.
 28. The bone screw of claim27, wherein the second interior perimeter surface includes a recess inat least a portion thereof, and each deformable member is adapted todeform outwards, when the cam is rotated relative to the head, to comeinto contact with the recess to fix the bone screw in orientationrelative to the implant member.
 29. The bone screw of claim 27, whereinthe bone screw includes grooves, at least a portion of which grooves arebrought into contact with the implant member when each deformable memberdeforms outwards to come into contact with the second interior perimetersurface.
 30. The bone screw of claim 25, wherein the implant member hasa top surface and a bottom surface, wherein the first region of theaperture is adjacent the bottom surface of the implant member, andwherein the second region of the aperture is adjacent the top surface ofthe implant member.
 31. The bone screw of claim 30, wherein the firstregion of the aperture tapers from wider to narrower in a directionmoving from the top surface of the implant member towards the bottomsurface of the implant member.
 32. The bone screw of claim 31, whereinthe bone screw is inserted from the top surface of the implant membertowards the bottom surface of the implant member.
 33. The bone screw ofclaim 30, wherein the bottom surface of the implant member is contouredto substantially match a contour of the bone to which the implant memberis affixed.
 34. The bone screw of claim 25, wherein the implant memberis used for performing at least one of: (a) fusing at least two bones;and (b) healing a fracture in a bone.
 35. The bone screw of claim 20,wherein the head of the bone screw includes a mechanism for engaging adriving tool.
 36. The bone screw of claim 35, wherein the mechanism forengaging the driving tool comprises a hex socket.
 37. The bone screw ofclaim 23, wherein the cam includes a mechanism for engaging a drivingtool.
 38. The bone screw of claim 37, wherein the mechanism for engagingthe driving tool comprises at least one lobe disposed adjacent thecentral opening.
 39. The bone screw assembly of claim 1, wherein thewasher is a split-ring washer.